The nexthop reveived for a prefix in a BGP update is cached in the

The nexthop reveived for a prefix in a BGP update is cached in the
nexthop cache in BGP and registered for resolution with the nexthop
tracking (NHT) component. If the prefix were to be received from the
same peer with a different nexthop, the prior nexthop needs to be
processed for cleanup and unregistered and removed from the cache, if
appropriate. That is handled with this patch.

Signed-off-by: Vivek Venkataraman <vivek@cumulusnetworks.com>
Reviewed-by:   Dinesh G Dutt <ddutt@cumulusnetworks.com>
Reviewed-by:   Donald Sharp <sharpd@cumulusnetworks.com>